SACO, Maine (AP) The cause of a rash of seal die-offs in Maine and New Hampshire likely won’t be known for at least a couple of weeks as sample collections and tests are still needed.

Southern Maine beaches have been beset with dead harbor seals in recent days, with dozens washing up stranded or having perished. The National Oceanic and Atmospheric Administration says Thursday sample collections still need to be completed, and then tests will take another two or three weeks or potentially longer.

NOAA says it’s possible multiple factors have played a role in the deaths, and they won’t know until results are in. Harmful algal blooms and avian flu are both potential causes.

This month has seen 133 dead harbor seals in Maine. NOAA says the average for August is 38.4.